CVE-2026-83609 xmldom: Creation-time XML Name/QName validation is bypassable via an embedded line terminator, allowing injection on the default serialization path
Attackers can inject malicious markup into XML documents via line terminators in names, leading to potential XSS or code execution in applications using xmldom.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-83609?
CVE-2026-83609 is a high-severity cross-site scripting vulnerability in @xmldom xmldom, published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. From 0.9.0 until 0.9.12, the shared reg() builder in lib/grammar.js compiles the anchored QName_exact validator with the multiline flag, so ^ and $ validate only one line instead of the complete name. createElementNS, createAttributeNS, createDocumentType, and createAttribute consequently accept a malformed XML name whose first line is valid and whose later text injects markup when serialized through either the default path or requireWellFormed: true. The triggering ECMAScript line terminators are U+000A, U+000D, U+2028, and U+2029. This issue is fixed in @xmldom/xmldom version 0.9.12.
Which versions are affected by CVE-2026-83609?
2 open source packages ship an affected version, including @xmldom/xmldom.
| Package | Affected | Fixed in |
|---|---|---|
@xmldom/xmldom npm | From 0.9.0 | 0.9.12 |
@xmldom/xmldom npm | From 0.9.0 | 0.9.12 |
How do I fix CVE-2026-83609?
Upgrade @xmldom/xmldom to 0.9.12 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-83609 being exploited?
There is no known exploitation of CVE-2026-83609 in the wild and no public exploit code.
Sources
Also known as CLSA-2026-1793108546, DEBIAN-CVE-2026-83609, GHSA-3px3-54cx-rmw9, ROOT-APP-NPM-CVE-2026-83609, UBUNTU-CVE-2026-83609.